This invention relates in general to form, fill, and seal packaging machinery of the type in which a continuous sheet of a packaging material is sequentially folded about a series of articles to be packaged, sealed about the articles, and cut into individually sealed packages. More specifically, this invention pertains to an improved crimper for heat sealing overlapping end portions of the sheet of packaging material after it is folded about an article.
The formation of a plurality of individually sealed packages of articles using a single continuous sheet of a packaging material is well known in the art. Briefly, the sheet of packaging material is initially passed through a folding mechanism, which continuously folds the film over on itself to form an enclosure for a series of spaced apart articles. The overlapping portions of the film are then sealed along a continuous longitudinal seal. Next, the folded sheet of packaging material is fed to a sealing and cutting assembly that seals the leading and trailing edges of the package to be formed about the enclosed article and cuts the tube into a plurality of individually sealed packages. In some instances, it is desirable to apply heat during the process of sealing the overlapping portions of packaging material. Packages produced by this form, fill, and seal process are commonly used for snack bars, candy, cereals, and the like, as well as for other non-food articles.
The sealing of the overlapping end portions of the sheet of packaging material is frequently accomplished by a mechanical crimping assembly. A conventional mechanical crimping assembly includes a pair of opposed crimpers that are disposed on opposite sides of the overlapping portions of the sheet of packaging material. The crimpers can include one or more heating elements to provide heat during the sealing process. The crimpers have undulating or serrated crimping surfaces defined by adjacent peaks and valleys. When the opposed crimpers are moved into engagement with the overlapping portions of the sheet of packaging material, the peaks of the first crimping surface are aligned with the valleys of the second crimping surface, and vice versa. Such engagement compresses the overlapping portions of the sheet of packaging material to form an intermeshing seal pattern.
During the crimping and sealing process, it is important that the crimpers exert a sufficient amount of force to compress the overlapping portions of the sheet of packaging material. If an insufficient amount of force is exerted by the crimpers, then the overlapping portions of the sheet of packaging material will not be compressed sufficiently to form a complete seal. At the same time, however, it is equally important that the amount of force exerted by the crimpers not exceed the strength of the sheet of packaging material. If an excessive amount of force is exerted by the crimpers, the sheet of packaging material will tear or break. Thus, it is desirable that the amount of force which can be exerted by the crimpers against the overlapping portions of the sheet of packaging material remain within a predetermined range to insure a complete and secure seal.
The distance between the opposed crimpers on the crimping assembly determines the amount of force exerted by the crimpers against the overlapping portions of the sheet of packaging material. In order to insure that the amount of force exerted by the crimpers remains within the predetermined desired range, the set-up of the crimpers on the crimping assembly must be performed very carefully. As a result, the set-up is a very time consuming operation.
It has been found that the heating element and the wires attached thereto are relatively fragile and are prone to failure. In the past, replacement of these components required removal of the crimper from the crimping assembly. This was relatively expensive process because of the set-up time required to replace the crimper on the crimping assembly. Sometimes, replacement of these components required replacement of the entire crimper, which incurred both the set-up time expense and the cost of the new crimper.
Recently, a crimper has been developed which does not require complete removal from the crimping assembly to replace the heating element. As shown in FIGS. 1 and 2, this crimper 10 includes a base 12 that is mounted on the crimping assembly and a top 14 that is removably attached to the base 12 with threaded fasteners 15. Respective grooves 16 and 18 are provided in the top 14 and the base 12 that define a bore 20 that extends longitudinally therethrough. A conventional heating element 22 (shown in FIG. 2) is disposed within the bore 20. The end of the heating element 22 is exposed at the opening of the bore 20, inasmuch as it is not protectively covered by any portion of the top 14 of the crimper 10. Electrical wires 24 attached to the end of the heating element 22 extend outside the bore 20. When it is necessary to replace the heating element 22, the top 14 is removed from the base 12, the heating element 22 is replaced, and then the top 14 is re-attached to the base 12. During this process, the base 12 remains mounted on the crimping assembly so that it is not necessary to perform a relatively time-consuming set-up operation after replacing the heating element 22. Unfortunately, the single heating element 22 in this crimper design does not always provide sufficient heat during a sealing operation. Another drawback is that the relatively fragile junction between the electrical wires 24 and the heating element 22 is left exposed in this design, as discussed above. Thus, it would be desirable to provide an improved structure for a crimper that addresses these drawbacks, while still avoiding the requirement for a relatively time-consuming set-up operation.